Jet ablation die singulation systems and related methods

ABSTRACT

Implementations of a method singulating a plurality of semiconductor die. Implementations may include: forming a pattern in a back metal layer coupled on a first side of a semiconductor substrate where the semiconductor substrate includes a plurality of semiconductor die. The method may include etching substantially through a thickness of the semiconductor substrate at the pattern in the back metal layer and jet ablating a layer of passivation material coupled to a second side of the semiconductor substrate to singulate the plurality of semiconductor die.

BACKGROUND 1. Technical Field

Aspects of this document relate generally to systems and methods usedfor singulating substrates. More specific implementations involvesemiconductor substrates.

2. Background

Semiconductor substrates are used to form a wide variety ofsemiconductor devices. The semiconductor devices are generallydistributed across a planar surface of the semiconductor substrate in aplurality of die. The plurality of die are separated from one anotherusing a singulation process like sawing.

SUMMARY

Implementations of a method singulating a plurality of semiconductor diemay include: forming a pattern in a back metal layer coupled on a firstside of a semiconductor substrate where the semiconductor substrateincludes a plurality of semiconductor die. The method may includeetching substantially through a thickness of the semiconductor substrateat the pattern in the back metal layer and jet ablating a layer ofpassivation material coupled to a second side of the semiconductorsubstrate to singulate the plurality of semiconductor die.

Implementations of a method of singulating a plurality of semiconductordie may include one, all, or any of the following:

The method may further include demounting the semiconductor substratefrom a first tape and mounting the semiconductor substrate to a secondtape.

Demounting the semiconductor substrate from the first tape may furtherinclude demounting after etching substantially through the thickness ofthe semiconductor substrate.

The method may further include mounting the semiconductor substrate to afirst tape after etching substantially through a thickness of thesemiconductor substrate.

Jet ablating the layer of passivation material may further include jetablating from the second side of the semiconductor substrate.

Jet ablating the layer of passivation material may further include jetablating from the first side of the semiconductor substrate.

Etching substantially through the thickness of the semiconductorsubstrate further includes plasma etching.

The thickness of the semiconductor substrate may be less than 50microns.

The thickness of the semiconductor substrate may be 25 microns.

The back metal may include a thickness between 1 micron to 15 microns.

The back metal may include a thickness between 1 micron to 3 microns.

Implementations of a method of singulating a plurality of semiconductordie may include forming a pattern in a back metal layer coupled on afirst side of the semiconductor substrate where the semiconductorsubstrate may include a plurality of semiconductor die. The method mayinclude mounting the semiconductor substrate to a first tape and etchingsubstantially through a thickness of the semiconductor substrate at thepattern in the back metal layer. The method may also include jetablating a layer of passivation material coupled to a second side of thesemiconductor substrate to singulate the plurality of semiconductor die.

Implementations of a method of singulating a plurality of semiconductordie may include one, all, or any of the following:

The method may further include demounting the semiconductor substratefrom the first tape and mounting the semiconductor substrate to a secondtape.

Demounting the semiconductor substrate from the first tape may furtherinclude demounting after etching substantially through the thickness ofthe semiconductor substrate.

Jet ablating the layer of passivation material may further include jetablating from the second side of the semiconductor substrate.

Jet ablating the layer of passivation material may further include jetablating from the first side of the semiconductor substrate.

Etching substantially through the thickness of the semiconductorsubstrate may further include plasma etching.

The thickness of the semiconductor substrate may be less than 50microns.

The thickness of the semiconductor substrate may be 25 microns.

The back metal may include a thickness between 1 micron to 15 microns.

The foregoing and other aspects, features, and advantages will beapparent to those artisans of ordinary skill in the art from theDESCRIPTION and DRAWINGS, and from the CLAIMS.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations will hereinafter be described in conjunction with theappended drawings, where like designations denote like elements, and:

FIG. 1 is a side view of a semiconductor substrate with a passivationlayer and a back metal layer thereon;

FIG. 2 is a side view of the substrate of FIG. 1 following patterning ofthe back metal layer;

FIG. 3 is a side view of the substrate of FIG. 2 following etching ofthe substrate material down to the passivation layer;

FIG. 4 is a side view of the substrate of FIG. 3 following demountingand mounting during jet ablation;

FIG. 5 is a side view of the two singulated die illustrated in FIG. 4following ablation of the passivation layer.

DESCRIPTION

This disclosure, its aspects and implementations, are not limited to thespecific components, assembly procedures or method elements disclosedherein. Many additional components, assembly procedures and/or methodelements known in the art consistent with the intended jet ablationsystems and related methods will become apparent for use with particularimplementations from this disclosure. Accordingly, for example, althoughparticular implementations are disclosed, such implementations andimplementing components may comprise any shape, size, style, type,model, version, measurement, concentration, material, quantity, methodelement, step, and/or the like as is known in the art for such jetablation systems and related methods, and implementing components andmethods, consistent with the intended operation and methods.

For semiconductor die that are less than 50 microns in thickness,particular processing challenges exist. Die handling, die strength, andperforming processing operations with the die all present specificchallenges, as die and wafer breakage can significantly reduce yieldand/or affect device reliability. Die strength is negatively affected bytraditional singulation options like sawing which induce die chippingand cracking along the die streets. These chips and cracks formed duringthe sawing process can eventually propagate during operation andreliability testing causing the die to fail.

Referring to FIG. 1, in various implementations disclosed in thisdocument, the semiconductor substrate 2 includes a plurality ofsemiconductor die 4 (two are subsequently illustrated in the drawings)that have been processed using a semiconductor fabrication process toform one or more semiconductor devices therein or thereon (not shown).Following the completion of the fabrication process (or during someportion of it, in some implementations), the semiconductor substrate 2is thinned on a side of the semiconductor substrate 2 that is oppositethe side on which the one or more semiconductor devices have been formedto a desired substrate thickness 6. The thinning process takes placeusing backgrinding, lapping, wet etching, any combination thereof, orany other technique for removing backside damage and/or the material ofthe semiconductor substrate 2 substantially uniformly across the largestplanar surface of the substrate. The semiconductor substrate 4 may be invarious implementations, by non-limiting example, single crystalsilicon, polysilicon, amorphous silicon, glass, sapphire, ruby, galliumarsenide, silicon carbide, silicon-on-insulator, and any othersemiconductor substrate type.

In various implementations, the thinning process may create an edge ringaround the wafer (like that present in the TAIKO backgrinding processmarketed by Disco Hi-Tec America, Inc. of Santa Clara, Calif.). The edgering acts to structurally support the wafer following thinning so thatno wafer carrier may need to be utilized during subsequent processingsteps. In various implementations, the thinning process may be carriedout after the semiconductor substrate 2 has been mounted to abackgrinding tape whether an edge ring is formed during backgrinding ornot. A wide variety of backgrinding tapes may be employed in variousimplementations, including those that are compatible with subsequentplasma etching operations.

Following the thinning process, the various die 4 formed in thesemiconductor substrate 2 need to be singulated from one another so theycan be subsequently packaged into semiconductor packages. In variousimplementations, following the thinning process a back metal layer 10 isapplied to the semiconductor die through, by non-limiting example,sputtering, evaporation, or another metal deposition process. In variousimplementations, the deposition process is conducted while the wafer iseither supported by an edge ring or supported by the backgrinding tape.In other implementations, however, the substrate may be demounted fromthe backgrinding tape and mounted to another support tape for subsequentprocessing steps.

FIG. 1 illustrates an implementation of a semiconductor substrate 2following the back metal deposition process and the thinning process. Invarious implementations, as illustrated, the substrate 2 is coupled witha tape 14 (which may be the backgrinding or other support tape invarious implementations). In other implementations, however, at thisstage in the process the wafer may not be coupled with a tape 14 (suchas when an edge ring is being used). As illustrated, the one or moresemiconductor die 4 (not yet separately visible) are covered by a layerof passivation material 16. In various implementations the passivationmaterial 16 may include, by non-limiting example, silicon nitride,oxides, metal electrical test structures, electrical test pads, silicondioxide, polyimides, metal pads, residual underbump metallization (UBM),any combination thereof, and any other layer or material capable offacilitating electrical or thermal connection between the one or moresemiconductor die and/or protecting the one or more semiconductor diefrom contaminants. Because of this, the term “passivation material” and“passivation layer,” as used herein, includes any of the aforementionedmaterials whether the material was deposited to act as a passivatingmaterial or whether the material merely forms a non-plasma etchableportion or layer in the die street region.

As illustrated in FIG. 1, the total thickness 8 of the semiconductorsubstrate 2 is the additive thickness of the substrate thickness 6, thethickness 18 of the back metal 10, and the thickness 12 of thepassivation material 16. In various implementations, thickness of theback metal may vary from between about 1 micron to about 15 microns. Inparticular implementations, the thickness of the back metal may bebetween about 1 micron to about 3 microns. In various implementations,the total thickness 8 of the semiconductor substrate 2 may be less thanabout 50 microns. In particular implementations, the total thickness 8of the semiconductor substrate may be between about 25 microns to about35 microns. In various implementations, the total thickness 8 may beabout 25 microns.

Referring to FIG. 2, the substrate 2 is illustrated following patterningof the back metal layer 10. The patterning may be accomplished using anyof a wide variety of photolithography processes involving theapplication of photoresist; exposure, development, then removal of thephotoresist; etching of the back metal 10 using an appropriate etchant,and removal of the photoresist. With the substrate material exposedfollowing etching and patterning of the back metal layer 10 in thepatterned areas/die streets 20 of the back metal layer 10, the materialof the substrate is ready for etching. In various implementations, thesubstrate material then be etched all the way down to or toward thepassivation layer 16. In other implementations, however, the etching maybe conducted partially through, or substantially through the thickness 6of the substrate 2 down to or toward the passivation layer 16 (theetching may be carried out using a plasma etching processes in variousimplementations). Generally, the plasma etch chemistries used to etchthe material of the substrate 2 do not etch the materials of thepassivation layer or any metal structures in the street (electricaltest/alignment features, etc.), leaving the plurality of semiconductordie still unsingulated after the etching of the substrate. Thesemiconductor die 4 following etching of the substrate 2 are illustratedin FIG. 3.

Referring to FIG. 4, the substrate 2 of FIG. 3 is illustrated afterhaving been demounted from the original (first) tape 14 and mounted to anew tape 22 (which may be a picking tape in various implementations). Asillustrated, the die 4 are still coupled together through at least thematerial of the passivation layer 16. In those implementations where thesubstrate has been only partially singulated or substantiallysingulated, some portion of the semiconductor material may also stillcouple the plurality of die together. For those implementations where anedge ring is used, the edge ring may still work to support the die 4during the demounting and mounting process. In some implementationswhere an edge ring is employed and the substrate is being processedwithout being mounted to a backgrinding tape, the substrate may beflipped over and mounted without first being demounted following theetching step.

FIG. 4 illustrates a fluid jet 24 being applied to the location of thestreet 20 between the semiconductor die 40, causing the material of thepassivation layer 16 (any other metal structures remaining in the street20) to ablate away. While water may be used as being the liquid used forablation, other fluids, gases, combinations of fluids, and combinationsof fluids and gases may be employed in various method implementations.

While in various implementations and as illustrated in FIG. 4, the fluidjet 24 is applied to the passivation layer side (second side) 26 of thesubstrate 2 after the substrate 2 has been flipped over followingetching of the substrate, in other implementations, the substrate 2 maynot be flipped over and the fluid jet 24 may be applied to the streetregion to ablate away the material of the passivation layer from theback metal side (first side) 28 of the substrate. While the substrate 2in FIGS. 2-4 is illustrated as having the full thickness 6 of thematerial of the substrate 2 etched through, in some implementations aspreviously discussed, a portion of the thickness of the substratematerial may be left unetched to add sufficient strength to thesubstrate to allow it to be demounted, flipped over, and mounted. Thejet ablation process may then be applied and used to remove thepassivation material and the remaining material of the substrate in thestreet 20 as well. In some implementations, however, the substrate 2 maynot be demounted and flipped over before application of jet ablation. Insuch implementations, it has been observed that the material of thepassivation layer is driven into the tape and successfully separates thevarious die under the pressure of the fluid jet.

Referring to FIG. 5, the semiconductor die 4 are illustrated followingjet ablation of the passivation material 16. They may now be picked fromthe support tape 22 and prepared for subsequent packaging operations.

As illustrated in FIGS. 2 and 3, the patterned back metal is used as thepatterning for the substrate etching process. Because of this, noadditional photolithographic processing may be needed to carry out thesubstrate etching process. In some implementations, however, aphotolithography step could be used to protect metal or other materialson the die during the jet ablation process. Also, because the materialof the semiconductor substrate 2 works to guide the flow of the waterduring the water jet ablation process (i.e., through resisting the flowof fluid, the substrate material causes the passivation material toyield under the pressure of the fluid stream or focuses the energy ofthe fluid stream on the passivation material), no additionalphotolithographic steps may need to be carried out to facilitate theablation process. This reduction in photolithographic steps reduces thenumber of total processing steps involving the wafer following thethinning process which can increase the overall yield of the processthrough reducing substrate breakage. Furthermore, because it is the jetablation used to finish fully clearing out the street areas, no specialdesigns (like drop out die and/or use of partial die) need to be addedto the design, thereby increasing total die per wafer. Furthermore, nospecial street designs that include no electrical test or alignmentfeatures may need to be used to enable the plasma substrate etchingprocess. Also, not using any saw singulating process may result inincrease in good die and increases in die strength due to reductions indie chipping and cracking induced during sawing processes.

In places where the description above refers to particularimplementations of jet ablation systems and related methods andimplementing components, sub-components, methods and sub-methods, itshould be readily apparent that a number of modifications may be madewithout departing from the spirit thereof and that theseimplementations, implementing components, sub-components, methods andsub-methods may be applied to other jet ablation systems and relatedmethods.

What is claimed is:
 1. A method of singulating a plurality ofsemiconductor die, the method comprising: forming a pattern using aphotoresist in a back metal layer coupled on a first side of asemiconductor substrate, the semiconductor substrate comprising aplurality of semiconductor die; etching substantially through athickness of the semiconductor substrate at the pattern in the backmetal layer; and jet ablating a layer of passivation material coupled toa second side of the semiconductor substrate to singulate the pluralityof semiconductor die.
 2. The method of claim 1, further comprisingdemounting the semiconductor substrate from a first tape and mountingthe semiconductor substrate to a second tape.
 3. The method of claim 2,wherein demounting the semiconductor substrate from the first tapefurther comprises demounting after etching substantially through thethickness of the semiconductor substrate.
 4. The method of claim 1,further comprising mounting the semiconductor substrate to a first tapeafter etching substantially through a thickness of the semiconductorsubstrate.
 5. The method of claim 1, wherein jet ablating the layer ofpassivation material further comprises jet ablating from the second sideof the semiconductor substrate.
 6. The method of claim 1, wherein jetablating the layer of passivation material further comprises jetablating from the first side of the semiconductor substrate.
 7. Themethod of claim 1, wherein etching substantially through the thicknessof the semiconductor substrate further comprises plasma etching.
 8. Themethod of claim 1, wherein the thickness of the semiconductor substrateis less than 50 microns.
 9. The method of claim 1, wherein the thicknessof the semiconductor substrate is 25 microns.
 10. The method of claim 1,wherein the back metal comprises a thickness between 1 micron to 15microns.
 11. The method of claim 1, wherein the back metal comprises athickness between 1 micron to 3 microns.
 12. A method of singulating aplurality of semiconductor die, the method comprising: forming a patternin a back metal layer coupled on a first side of a semiconductorsubstrate, the semiconductor substrate comprising a plurality ofsemiconductor die, wherein the pattern is formed through aphotolithography process; mounting the semiconductor substrate to afirst tape; etching substantially through a thickness of thesemiconductor substrate at the pattern in the back metal layer; and jetablating a layer of passivation material coupled to a second side of thesemiconductor substrate to singulate the plurality of semiconductor die.13. The method of claim 12, further comprising demounting thesemiconductor substrate from the first tape and mounting thesemiconductor substrate to a second tape.
 14. The method of claim 13,wherein demounting the semiconductor substrate from the first tapefurther comprises demounting after etching substantially through thethickness of the semiconductor substrate.
 15. The method of claim 12,wherein jet ablating the layer of passivation material further comprisesjet ablating from the second side of the semiconductor substrate. 16.The method of claim 12, wherein jet ablating the layer of passivationmaterial further comprises jet ablating from the first side of thesemiconductor substrate.
 17. The method of claim 12, wherein etchingsubstantially through the thickness of the semiconductor substratefurther comprises plasma etching.
 18. The method of claim 12, whereinthe thickness of the semiconductor substrate is less than 50 microns.19. The method of claim 12, wherein the thickness of the semiconductorsubstrate is 25 microns.
 20. The method of claim 12, wherein the backmetal comprises a thickness between 1 micron to 15 microns.